1. Field of the Invention
The present invention relates to an electric rotating machine comprising a shaft seal device which cools an electric rotating machine main body with a cooling medium such as hydrogen gas and which seals a shaft through portion.
2. Description of the Related Art
In a large capacity turbine generator, for example, pressurized hydrogen gas is sealed inside the machine, and a rotor and a stator which configure a generator main body (electric rotating machine main body) are cooled using the hydrogen gas. Because the hydrogen gas has lower density and higher specific heat capacity than air, hydrogen-cooled generator can operate in high efficiency. Therefore, many large capacity turbine generators use this cooling system. In such a hydrogen-cooled generator, shaft seal devices for preventing leakage of the hydrogen gas inside the machine, from bearings to the outside are installed at both ends of the generator (see (Prior art publication 1: Jpn. Pat. Appln. KOKAI Publication No. 7-75291) and (Prior art publication 2: Jpn. Pat. Appln. KOKAI Publication No. 10-14158)).
Now, a conventional shaft seal device will be explained with reference to the drawings. FIG. 28 is a cross-sectional view of an end of an electric rotating machine in the vicinity of a shaft seal device 99 that seals hydrogen the inside of a machine in a conventional hydrogen-cooled electric rotating machine. Reference numeral 1 is a stator frame which has a cylindrical shape, and at an end thereof, an end bracket 3 is fixed via a stator frame end plate 2. A bearing bracket 4 is fixed on the end bracket 3, a bearing stand 5 is attached inside the bearing bracket 4, and a bearing device (bearing) 6 is attached inside the bearing stand 5. The bearing 6 supports a rotating shaft (shaft) 7 to be rotatable.
A seal casing 9 and a seal ring 10 which configure the shaft seal device 99 are provided to seal hydrogen gas 8 inside the machine that is enclosed by the stator frame 1, the stator frame end plate 2, the end bracket 3 and the like not to leak from a gap formed with the rotating shaft 7 which rotates due to the movement of the electric rotating machine. In addition, oil deflectors 11 and 12 are provided inside the machine and outside the machine, respectively, such that a lubricating oil used in the shaft seal device 99 and the bearing 6 does not leak, and a space called a seal cavity 13 is provided between the internal oil thrower 12 and the shaft seal device 99.
FIG. 29 is an enlarged view showing the details of the seal casing 9 and the seal ring 10 which configure the shaft seal device 99. In FIG. 29, the seal ring 10 comprises two seal rings 10A and 10B which are aligned in the axial direction, and each of the seal rings is processed such that the inner diameter is slightly larger than the outer diameter of the rotating shaft 7.
Seal oil 17 is supplied from the seal casing 9 with slightly higher pressure than the gas pressure of the hydrogen gas for generator cooling. The sealing oil 17 is supplied to a narrow gap 19 which is formed by the seal rings 10A and 10B and the rotating shaft 7 via an axial direction gap 18 between the seal ring 10A and 10B. By forming an oil film here, leakage of the hydrogen gas 8 inside the machine to the outside the machine is prevented. A spring 20 presses the seal rings 10A and 10B, and adjusts a circumferential direction gap 19 between the rotating shaft 7 and the seal ring 10A and 10B.
FIG. 30 is a cross-sectional view along the arrow 30-30 in FIG. 29, and the seal ring 10B is formed of a seal ring upper half portion 10Ba and a seal ring lower half portion 10Bb which form a radial arc in the axial direction with respect to the rotating shaft 7. The seal ring 10A is same as the seal ring 10B.
The spring 20 is fixed by screws 20a provided in the seal casing 9. The spring 20 is disposed in an annular state along the joint between the seal ring 10A and the seal ring 10B, and forms the circumferential direction gap 19 with the rotating shaft 7 with an optimal pressing force. An optimal amount of oil is supplied by adjusting the circumferential direction gap 19 to fill the circumferential direction gap 19 with the sealing oil 17 and the hydrogen gas 8 can be sealed inside the machine.
The sealing oil 17 which has flowed outward from the circumferential direction gap 19 flows to the seal cavity 13 side and the bearing device side. The sealing oil 17 which has flowed outward to the seal cavity 13 side is recovered alone or alternatively, the sealing oil which has flowed out to the bearing device side is recovered together with the lubricating oil from the bearing device 6. Each of the oils recovered are combined again after collection, and as shown in FIG. 31, they are pressurized using a pressure pump 59 and sent to the shaft seal device and the bearing device, respectively. However, the sealing oil 17 which has flowed from the circumferential direction gap 19 to the bearing device 6 side and the lubricating oil from the bearing device are surrounded by air, and thus return to the pressure pump 59 in a state in which air is mixed in the oil. Because the oils are sent to the shaft seal device after pressure is applied, part of the air mixed into the sealing oil 17 that has flowed from the circumferential direction gap 19 to the seal cavity 13 side blows out to the seal cavity 13 side. Instead, the hydrogen gas 13 inside the machine which is inside the seal cavity 13 is mixed with the seal oil 17 and discharged outside the machine. The air blown into the seal cavity 13 replaces the hydrogen gas 8 inside the machine via the gap between the deflector 12 and the rotating shaft 7, and as a result, the purity of the hydrogen gas 8 inside the machine is lowered.
In order to avoid this, in the typical shaft seal device, the oils are subjected to degassing in a degassing device 58 before entering the pressure pump 59, and the oils are supplied to the shaft seal device or the bearing device 6 in a state in which gas such as the cooling hydrogen gas 8 or air is not mixed in the oils.
However, the suction processing device 58 is of a comparatively high cost, and this is one factor causing increased cost for the electric rotating machine in which hydrogen gas or the like is used as the cooling medium.
It is to be noted that in FIG. 31, aside from the above-described configuration, the dynamo-electrical machine main body may be contained in the frame or it may comprise a hydrogen extracting device 55 which extracts hydrogen gas circulating in a circulating system (not shown), an air extracting device 56 for extracting air from the lubricating oil in the shaft seal device 6, a lubricating oil system 57 for sending the lubricating oil from which air has been removed to the degassing device 58 and the bearing device 6.
Aside from the prior art example of the shaft seal device described above, there is also a non-contact type sealing device configured as follows. As shown in, for example, FIG. 28, the seal ring 10 is contained inside the seal casing 9 attached to the end bracket 22, and the spring 20 is supported so as to form a narrow gap between itself and the rotating shaft 7. The seal rings 10 are arranged in 2 rows in the axial direction of the rotating shaft 7, and oil of a pressure that is slightly higher than the gas pressure inside the machine is supplied from the outside to the gap between the sealing 10 and the rotating shaft 7. The pressure oil passes through the gap, and the gas inside the machine is sealed due to the formation of leaking oil as shown by the arrow in FIG. 29. In this type of configuration, because the seal ring 10, the seal casing 9 and the rotating shaft 7 etc. are thermally deformed in a complex manner during operation, the seal oil amount (purge oil amount) may exceed a design value and sometimes increases more than expected in transition (particularly at the time of startup). Furthermore, the thickness of the oil film decreases locally due to deformation, and vibration is caused by the frictional force of that portion. In recent years, development of a brush type contact seal for solving these problems has been progressing, and this is being used as an air seal for a gas turbine or steam turbine, a liquid seal for low pressure difference, or a dust-protective seal. However, in a liquid seal for high pressure difference using a liquid as the sealing medium (purge oil), such as in a gas sealing inside the turbine generator, sufficient sealing properties can not be obtained, and further, a large amount of sealing oil is necessary.
Aside from the prior arts described above, there are also Prior art publication 3 (Jpn. Pat. Appln. KOKAI Publication No. 2002-81552), Prior art publication 4 (Jpn. Pat. Appln. KOKAI Publication No. 2003-161108), Prior art publication 5 (Jpn. Pat. Appln. KOKAI Publication No. 2002-303371) and Prior art publication 6 (Jpn. Pat. Appln. KOKAI Publication No. 2001-90842).
In Prior art publication 3, a rotating body like a rotating shaft has an improved brush sealing device which is provided at a portion that penetrates a pressure partition wall and is described as follows. That is, this example describes the brush seal device having a structure with “a plurality of brush seal segments that are divided in the circumferential direction”, in order to disassemble the device and to facilitate the removal of the internal rotating shaft at the time of manufacture, or at the time of inspection after operation has begun. However, there is no description of any measures for dealing with possible dropping of the brush seal due to the pressure of the leaking oil.
Prior art publication 4 merely describes a structure for facilitating attachment and removal in the installation method for a sealing device and for preventing installation error. In this sealing device, a labyrinth seal is used together with a brush seal in order to improve the sealing properties of the rotating shaft in a turbo device having a labyrinth seal. Prior art publication 4 is a labyrinth seal, and the labyrinth seal is a sealing mechanism which suppresses the leakage of fluid from the high pressure side to the low pressure side with the labyrinth seal interposed therebetween, and is different from the oil deflector which is disposed with the bearing interposed therebetween. Basically, in the oil deflector, the fluid pressure at both sides where the oil deflector is nipped is the same and it does not limit the amount of fluid leakage. In addition, the purpose of the oil deflector is to prevent or suppress the leakage of mist oil or liquid oil and it is thus different from the labyrinth seal.
Meanwhile, in the Prior art publication 4, operational effects of the labyrinth seal are described in which sealing properties are improved by providing a back plate at the high pressure side of the labyrinth seal and at the low pressure side of the brush seal, or alternatively, the sealing properties are improved by attaching a brush seal to both sides of the labyrinth seal, but this is different from the oil deflector.
The Prior art publication 5 describes a device in which oil mist (oil particles in a mist-like state) is sealed in a bearing cavity. In order to seal the oil mist that is generated in the bearing cavity inside the bearing cavity, the bearing cavity may be attached to one side of the bearing housing or at the side surfaces at both sides. Thus, while Prior art publication 5 seals oil mist (oil particles in a mist-like state) inside the bearing cavity, one is the type in which the liquid oil (usually called side leak) that is blown out from the side surface of the bearing and the sealing oil of the shaft seal device that uses the oil which seals the gas inside the machine are separated (not caused to contact each other), and the other one is the type in which all the oils used in the machine (sealing oil and bearing oil) are cut-off so as not to contact the outside air. Thus, both types are not necessarily provided at the bearing side surface.
Prior art publication 6 describes that a special kind of brush (in which extremely fine fibers are woven) is used to reduce the leakage of fluid, and there is no abnormal charge which is different from that of a metal brush, and no breakage as in the case of the metal brush and the ceramic brush. However, the brush seal that uses this special kind of brush is attached to a machine having a pressure difference between the inside and the outside the machine, and it clearly different from one that basically does not seal a pressure difference.